Various storage systems comprise a controller that stores data in one or more memory devices. Certain storage operations such as program and erase operations require a high operating voltage, e.g., on the order of 12V, which may be provided to the memory devices from an external power supply. Alternatively, the memory devices may comprise an internal charge pump that converts a low voltage input to the required high operating voltage.
Memory devices comprising a charge pump are known in the art. For example, U.S. Pat. No. 6,597,603, whose disclosure is incorporated herein by reference, describes a dual mode high voltage power supply circuit using an external high voltage connected through an internal high voltage switch, which determines whether the memory blocks of a non-volatile memory circuit are programmed in a first mode from an internal high voltage charge pump or are programmed in a second mode from an external high voltage power supply connected in parallel to the internal high voltage charge pump.
U.S. Pat. No. 6,240,027, whose disclosure is incorporated herein by reference, describes a chip containing a Flash memory in which external high voltages are connected to selected cells to be erased. Internal pump circuits contained on the chip are turned off while the external voltages are used. The external voltages, a high negative voltage and a high positive voltage, are connected to gates and sources respectively of selected cells to be erased by a voltage control module. The external voltages are used during manufacture during program/erase operations to perform the erase function efficiently. The internal high voltage pump circuits are used to erase flash memory cells after being assembled on a circuit board by a user.